The goal of this project is to create a stable murine myeloma cell line which secretes a human antibody against anthrax exotoxin. The molecular cloning of human immunoglobulin (Ig) genes from the genomic DNA of a human/mouse hybridoma is proposed. The human Ig genes, which encode an antibody against anthrax exotoxin, will be spliced to previously characterized mouse Ig genes. The resulting chimeric Ig genes containing murine transcriptional signals and human Ig coding regions will be transfected into a non-producing murine myeloma cell line. The transfected cells will then be screened for those producing human antibodies against anthrax exotoxin. Characterization and scale up of the cell line created in phase I as well as the anti-anthrax antibody it produces will result in a valuable product. Furthermore, the data obtained should apply to succeeding cell lines created by transfecting different Ig genes into the same murine myeloma recipient. This technology allows one to express an endless series of different human antibodies in the same murine myeloma cell line. Furthermore, it allows one to produce novel antibodies such as chimeric mouse/human antibodies in the same murine myeloma cell line.